Interposers are used for integrated circuit packaging, typically for space transformation, which is for routing connections between semiconductor dies and packaging components. FIG. 1 illustrates a cross-sectional view of a portion of an interposer 10. Usually, interposer 10 includes a substrate 30, which is typically formed of organic materials or ceramics. One or more through-silicon vias (TSVs) 50 are formed in the substrate 30 for making electrical connections from one or more semiconductor dies and/or packaging components (not shown).
With the increasing scaling down of integrated circuits and increasing circuit functionality there is an increased demand for progressively smaller linewidths on the interposer. As linewidths shrink, RC transmission line effects increase due to loading from die/die package resistance, inductance, and/or capacitance. Moreover, as substrate 30 is not grounded cross coupling or cross talk between adjacent TSVs increases as well. Due to this cross-coupling between TSVs, signals traveling along relatively long interconnections suffer delays and other forms of distortion. As a result, these signals may become corrupted, slowing operation of integrated circuits or even causing failure. These effects are more pronounced as operating frequencies increase.